1. Field of the Invention
The invention concerns a two-phase soap bar defined by a clear and opaque area and a process for production thereof.
2. The Related Art
Soap bars which are clear have a certain aesthetic appeal to consumers. Often consumers associate clarity with "naturalness" which is a sought after benefit. Consequently, there is a demand for clear soap bars.
Bars of varying clarity, form and other physical properties have been described in the literature. Methods of manufacture are numerous and varied.
One of the earliest patents in the area is that of U.S. Pat. No. 2,820,768 (Fromont) which describes a transparent, substantially non-alkaline soap formed from a mixture of alkali metal soap and the reaction product between a free fatty acid and triethanolamine. The components are mixed together under heating at 100.degree.-120.degree. C. to obtain a homogeneous clear mass which is maintained upon cooling. This mass is poured into frames, cooled, cut and pressed into cakes or bars. Fromont is the basis for the bar product known as "Neutrogena".
U.S. Pat. No. 5,041,234 (Instone et al.) describes bars of high soap content that include a solvent system of water, triethanolamine and polyols. U.S. Pat. No. 3,793,214 and U.S. Pat. No. 3,926,828, both to O'Neill, describe utilizing mixtures of alkaline sodium compounds and alkanolamines to neutralize free fatty acids to obtain a glossy surface appearance even after repeated use of the product.
Japanese Patent 61/155499 (Hara) formulates amino acids in place of alkanolamines to achieve similar fast drying times but with the added benefits of avoiding stickiness resulting from hygroscopicity and of good lathering. U.S. Pat. No. 4,206,069 (Borrello) overcomes the surface stickiness problem through careful selection of soap, detergent and solvent concentrations. U.S. Pat. No. 4,988,453 and U.S. Pat. No. 5,002,685, each assigned to Chambers et al., disclose translucent detergent bars based on a composition of soap, mono- and dihydric alcohols and water. Sugars (i.e. sucrose, fructose or glucose), cyclic polyols (i.e. glycerol, sorbitol or mannitol) and polyalkylene glycols were found useful as further components.
Several patents advocate special additives. U.S. Pat. No. 4,493,786 (Joshi) details use of lanolin and lanolin derivatives for inhibiting crystallization of soap thereby promoting clarity. U.S. Pat. No. 4,468,338 (Lindberg) fortifies a bar with sulfites to prevent progressive darkening upon storage. U.S. Pat. No. 4,741,854 (Krupa et al.) inhibits discoloration through a combination of sulfite and hydride compounds. U.S. Pat. No. 3,969,259 (Lages) discovered germicide could be incorporated into a milled transparent soap without any opacifying effect. The germicide must, however, be first dissolved in a perfume material. The perfume solution is then added to the composition at any point between drying of the soap chips and extrusion thereof through a plodder.
In a more unusual approach, U.S. Pat. No. 4,517,107 obtains a translucent product through use of a cavity transfer mixer that shears the soap.
Finally, there is U.S. Pat. No. 4,504,433 (Inui et al.) describing a soap article containing dried shapes also formed of soap. The process reported therein includes the steps of placing on a bottom of a cylindrical frame a supporting base of transparent soap which has been cooled to solidification but has not yet been dried. The base has a height lower than that of the frame. Thereafter a dried shape of colored soap is placed onto the supporting base. A dough of transparent soap which may or may not be colored is then poured into the frame followed by heating the resultant composition to a molten state. Upon cooling, the solidified transparent soap that results is removed from the frame and further dried.
Beyond the purely transparent bar technology, there have been toilet bars, especially perfume soaps, sold in the Orient, which were a combination of clear and opaque portions. These bars are formed by gluing one surface of a typical extruded opaque soap onto a congruent surface of a cast clear bar. Opaque and clear portions are of different formulations with mostly different ingredients and where the ingredients are identical, the concentrations are often different. The opaque portion is usually produced through the very rapid process of plodding through an extruder while the clear portion requires the much slower casting method of production. A problem with this technology is that wear (i.e. use rate) may be different between different portions of the bar. Additionally, there is limited latitude for providing curvilinear shapes with the known technology.
Even with the aforementioned difficulties, there is great appeal to a two-phase soap. Active ingredients that may be harmed by ultraviolet light can be formulated in the opaque phase. Other ingredients which may be stimulated through light may preferentially be incorporated into the clear phase. Of course, aesthetics can be much more pleasing in a dual phase system. In view of these considerations, it is evident that the art awaits a major advance in this area of technology.
Accordingly, it is an object of the present invention to provide a dual-phase toilet bar of particularly pleasing aesthetics.
Another object of the present invention is to provide a dual-phase toilet bar that functions similar to a plodded conventional opaque soap in its cleansing activity yet has an area which, through mildness, can provide skin benefits associated with clear-type bars.
A further object of the present invention is to provide a dual-phase toilet bar wherein certain active ingredients are incorporated into one phase but not the other.
A still further object of the present invention is to provide a process for manufacturing a dual-phase toilet bar wherein a curvilinear shape is obtainable.
These and other objects of the present invention will become more apparent from the summary, detailed description and example which follow.